Device for producing three-dimensional models with special building platforms and drive systems

ABSTRACT

The invention relates to a device for producing three-dimensional models in a continuous process, comprising a build surface which has a first end in the direction of movement and a second end in the direction of movement, at least one dosing device and at least one solidification unit, characterized in that the build surface is designed to transport heavy components, and the components are transportable over the build surface essentially without distortion, and also comprising a method therefor.

CLAIM OF PRIORITY

This application is a continuation of U.S. patent application Ser. No. 14/400,957 filed on Mar. 13, 2015 which is a 371 of PCT Application serial number PCT/DE2013/000271 filed on May 17, 2013, and claims priority therefrom. This application further claims priority from German Patent Application number DE102012010272 filed on May 25, 2012. The contents of U.S. patent application Ser. No. 14/400,957, International Patent Application PCT/DE2013/000271 and German Patent Application DE102012010272 is each incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a system for the continuous production of three-dimensional models on a horizontal transport device, using a layering technique.

PRIOR ART

In layering methods used today for producing three-dimensional objects based on computer data, methods are used in which a platform (building platform), which is movable at least in the vertical direction and which, if necessary, is surrounded by a container and thus forms a job box, is placed in an uppermost position at the beginning of the process. A build material, for example a substance in the form of particulate material in the case of 3D printing or laser sintering, is then applied in a thin layer over the entire area of this platform. In another step, the material is selectively bound with the aid of a physical or chemical solidification mechanism according to the desired component shape. This binding step may take place, for example, using adhesives, which may be printed with the aid of ink jet techniques. The platform is then lowered by one layer thickness, and a new layer of particulate material is applied.

These steps are repeated until the desired body is built, i.e., all necessary layers have been applied and solidified. The container is successively filled with particulate material during these steps, parts thereof being bound to the desired structural body, while the rest remains loose and is used during the building process as a support medium for overhanging parts of the object to be built.

After completing the layering process, following a waiting period which may be necessary, the loose particulate material may be extracted or removed in another manner and the desired object discharged.

It is possible in this case to produce components continuously using an endless, horizontal layer feed.

In conventional systems for building models in layers, the components are produced vertically in layers from top to bottom.

When the maximum build height of a system is reached, the building process must be stopped in order to subsequently remove the components in the system and thereby create space for a building process, or another build frame must be inserted with the aid of a changing system in order to be able to thereby start a new building process. As a result, the construction of components is limited with respect to size and productivity.

In the known “continuous 3D printing” method, the layer feed takes place in the horizontal direction, e.g., on a continuous conveyor belt.

Gravity prevents a layer to be applied perpendicularly to the layer feed, which is why the individual layers are applied at an angle. The angle is selected in such a way that it is smaller than the specific angle of repose of the corresponding particulate material.

The layering process is followed by an enclosed conveyor line, whose length is adapted to the method-dependent hardening duration. At the end of the conveyor line, the finished components enter a removal area. There, the components are freed of unbound particle material and removed without having to interrupt the production of additional parts.

In the continuous method, different tools and methods may be used to feed the components, for example continuous conveyor belts are used.

Continuous conveyor belts are generally closed belts made of a flexible material (e.g., woven fabric) that is looped around a drum at each end to reverse the direction of travel. At least one of the two drums drives the conveyor belt. Between the drums, the belt must be pulled over a supporting surface to avoid sagging. Above a certain width of the conveyor belt or above a certain mass of the particulate material feedstock, the frictional engagement between the conveyor belt and the supporting surface is so great that stick/slip effects may occur, or the drive may fail completely.

Link conveyors are furthermore known, which are able to accommodate very high loads. Link conveyors of this type are driven in the same way as conveyor belts. A drive drum or return drum is located at each end of the closed link conveyor. If a link conveyor is driven in this manner, an uneven feed results. This is because the plates unwind in the manner of a polygon. At the same time, the bearing of the individual links may prove to be sensitive to contaminants. If the links do not ideally abut each other, build material may enter the space between two plates via the joints and impair the operation of the flexible connection. In addition, particulate material may be lost uncontrollably via the joint, which may result in defects in the particulate material feedstock and thus in the components.

Link conveyors are an additional option. Link conveyors are able to accommodate high loads and are driven in the same manner as conveyor belts. A drive drum or return drum is located at each end of the closed link conveyor. If a link conveyor is driven in this manner, an uneven feed results. This is because the plates unwind in the manner of a polygon. At the same time, the bearing of the individual links may prove to be sensitive to contaminants. If the links do not ideally abut each other, build material may enter the space between two plates via the joints and impair the operation of the flexible connection. In addition, particulate material may be lost uncontrollably via the joint, which may result in defects in the particulate material feedstock and thus in the components.

The use of individual plates which are fed in a feed unit from a magazine is also known. In this case, the build time is dependent on the number or length of the individual plates. Continuous building is possible only if the building platforms are automatically returned to the magazine at the end of the building process. This is technologically complex, since the plates must, among other things, be clean for reuse. The vibration-free and dense placement of a new plate has also proven to be difficult. The concept of this building device must furthermore be changed to the extent that the coater is no longer able to travel under the level of the build plane.

The known feeding means for use in a continuous process for building bulky and complex models (components) in layers are thus subject to a large number of problems. Up to now, no devices and methods are known which are suitable for producing large and heavy models and which avoid the disadvantages described above.

A need thus exists for providing a device and a method for building models in layers by means of which large and heavy components may be produced, preferably in the continuous process, and which are consistent with a preferably precise satisfaction of the requirements, or by means of which the disadvantages of the prior art may be at least improved or avoided entirely.

PREFERRED EMBODIMENTS OF THE INVENTION

The invention relates to a device for producing three-dimensional models, preferably in a continuous process, comprising a build surface which has a first end in the direction of movement and a second end in the direction of movement, at least one dosing device and at least one solidification unit, characterized in that the build surface is designed to transport heavy components, and the components are transportable over the build surface essentially without distortion. In preferred embodiments which provide a rotational operation, the first end is understood to be the start of the process, and the second end is understood to be the end of the process, or preferably the unpacking position or the unpacking operation.

The inventors have advantageously succeeded in providing drives which are suitable for producing bulky and heavy components, in particular in continuous processes, for building models in layers using inclined printing, and which facilitate precise production without distortion in compliance with the requirements.

The inventors thus have developed a device and a method, by means of which particularly heavy components may be precisely produced in the continuous layering method (inclined printing) and which avoid or at least significantly improve the disadvantages of the prior art. In one preferred embodiment, the work takes place in batches.

As illustrated above, different options exist for transporting the particulate material strand. However, the systems all have serious problems with regard to precision of the movement under heavy loads. A conveyor belt must thus be guided over at least two return rollers, the drive being reasonably integrated into the rear return roller in the conveyance direction. The movement precision of the belt would be highest in this location and correspondingly lowest at the other end, due to slackness in the belt. However, this is where the layering is carried out, i.e., the very place where the belt movement must be precise.

With the aid of the device according to the invention and the method according to the invention, it is now possible to move the feedstock completely forward and to achieve a distortion-free, precise feed when producing heaving components. Disadvantageous distortions due to slackness in the drive, which occur in known methods and systems used therein, are advantageously avoided with the aid of the invention. The precise production of heavy components by means of layering in the continuous process is made possible hereby.

In preferred devices according to the invention, the build surface is a horizontal, continuous and/or open conveyor belt, or it is designed as a rotating platform or a step conveyor.

The build surface—and thus, in particular, the model or component—is preferably conveyable with its first and second ends essentially at the same speed and with the same feed.

A particularly preferred device is characterized in that the deviation in the feed between the first and second ends of the building platform is less than 1 mm, preferably less than 0.5 mm, most preferably 0.3 mm.

Preferred devices according to the invention may be characterized in that the conveyor belt rests and runs on continuous and/or lateral rollers.

A device according to the invention may furthermore be characterized in that the conveyor belt has at least one central support, the support preferably comprising air cushions and/or friction bearings and/or rollers and/or ball casters.

The conveyor belt may have individual links, preferably connected by hinges, the links having gripping elements which are driven by worm gear or guide mechanisms.

The gripping elements may be gripped and positioned with the aid of horizontally positionable or oscillating or rotating grippers and/or barbed hooks and/or magnets and/or vacuum grippers.

One area of the conveyor belt may be transported on a liftable base by means of frictional engagement or cohesion of solid bodies.

The conveyor belt is preferably driven by at least one continuous roller or on both sides by at least two lateral rollers.

In another preferred device, one area of the conveyor belt is transported by means of magnetic fields.

It is also possible for the building platforms of the device to be automotively driven, preferably on overhead rails or free-moving.

The hinges contained in the device preferably have only limited mobility perpendicularly to the conveyance direction.

Roller tracks are preferably added to the device.

The device according to the invention is particularly preferably characterized in that a horizontal, movable build surface for applying build material is provided, and a build space is disposed around it, on which at least one dosing device for particulate material and a solidification unit for particulate material are mounted via linear guides, and the horizontal build surface [is provided] in a Z direction, i.e., at a certain angle to the transport device which is smaller than the angle of repose of the build material. The angle is preferably <30 degrees.

Another aspect of the invention is a device referred to as a “cone printer” for building components. Its functionality is apparent, in particular, from FIGS. 10a through 10 c.

A cone printer in the sense of the invention is able to build components on a building platform in a rotating and outwardly directed motion from the inside to the outside by layering particulate material.

The production of components takes place according to the 3D method, i.e., a layer of particulate material is applied in the first step, and a selective solidification of the particulate material takes place in the second step in the known manner. The application of particulate material takes place continuously, a coater (1) completing a circular path for layering the particulate material. The solidification unit (2) follows this path of the coater (1) and ensures the selective solidification of the particulate material and thus the production of components.

A plurality of components may be advantageously produced on one building platform simultaneously or in batches.

The building platform may be selected in dimensions that allow heavy components to be produced. This preferred design thus also achieves the object of a distortion-free production of multiple components.

The special advantage of the use of a cone printer lies in the fact that large and heavy components may be produced without distortion, and a plurality of components may be produced with a high degree of precision in batches.

The invention furthermore relates to a method for producing three dimensional models in the continuous process, comprising the following steps: a. building the model in layers on a building platform in a first position, a first layer being applied; b. transferring the model from the first position to a second position with the aid of a feed after a layer is built, the building platform, which has a first front end and a second rear end, being transported with the model; c. building another layer on the model on the building platform; d. transferring the model on the building platform to another position; repeating steps a.) through d.), the transfer preferably being carried out by means of a step conveyor, the step conveyor preferably having lifting and thrusting grates.

In the method according to the invention for producing three-dimensional models, the model on the building platform is transferred without distortion from the first position to the second position.

The method according to the invention for producing three-dimensional models is characterized in that the building platform with the model is evenly transferred from the first position to the second position and any further position essentially without deviations in feed between the first and second ends of the building platform.

The deviation in feed between the first and second ends of the building platform from the first position to the second and any further position is preferably less than 1 mm, preferably less than 0.5 mm and most preferably less than 0.3 mm.

When producing large and heavy components, in particular, the requirements of the horizontal transport device of devices for the continuous method are particularly critical in order to achieve a dimensionally accurate and precise reproduction in the component.

In this case, a loosely applied feedstock made of sand or particulate material must be positioned a few micrometers (e.g., 80 μm) with each new layer. The feedstock has only a limited stability and may weigh several tons.

The device according to the invention or the conveyor system according to the invention is preferably characterized by one or all of the following characteristics:

Continuous feed (continuous conveyor)

Vibration-free feed

High positioning accuracy in the range of just a few micrometers (e.g., 1 μm)

High rigidity in the conveyance direction under high loads (tensile loads up to several tons)

High rigidity in the vertical direction (weight load up to several tons)

Resistance of the supporting surface to contamination with the build material (e.g., abrasive sands/particulate material or aggressive solvents)

Density of the supporting surface in order to prevent runoff of the build material.

No stick-slip effects

Minimal maintenance with almost non-stop operation

Cost-effective construction

The present invention advantageously combines the aforementioned characteristics or at least a subcombination thereof and thus provides an advantageous device and a method for building models in layers, the disadvantages of known devices and methods being avoided or at least partially improved.

In particular, with regard to load tolerance and positioning accuracy, the invention provides a superior device and method.

The device according to the invention may be used, for example, to produce casting molds from molding sand, in which the dimensions and thus the weight of the particulate material feedstock are particularly high.

One approach according to the invention lies in the use of link conveyors. Link conveyors whose individual links are connected by special hinges are particularly suitable in this case. The hinges have a stop which results in the fact that the link conveyor is able to bend or roll off from the plane in only one direction (downward in this case). It is rigid in the other direction (upward in this case). A sagging of the link conveyor is prevented thereby, and an even feed with only slight deviations or only slight distortion is achieved.

In one particularly preferred embodiment, this link apron is laid over a roller track and driven by friction engagement. The roller track is an arrangement of multiple rollers or cylinders. One, multiple or all rollers may be driven. If all rollers are driven, an even feed of the link conveyor results. Since the entire build space of the link conveyor is driven, the belt does not undergo any tensile loading. The belt is thus unable to lengthen during operation, and stick-slip effects are ruled out. If the link conveyor has play in the hinges, this does not have any negative effect.

This type of drive also ensures an exact positioning, since the drive takes place at the point where the plates have already achieved a horizontal alignment. A polygon effect, which occurs in known systems, does not take place in the invention.

The individual rollers or cylinders may be preferably synchronized by means of coupling elements such as toothed belts, driving belts, chains, toothed wheels or worm gears. If the rollers are connected by driving belts, toothed belts or chains, the link conveyor may also rest directly on the driving belts, toothed belts or chains. Particularly wide belts require rigid cylinders or cylinders having a large diameter for support. As the cylinder diameter increases, so does the distance between the individual cylinders. Link aprons having low intrinsic rigidity could sag between the cylinders.

It may thus be reasonable to attach the drive only to the sides of the link conveyor and to separately support the free-hanging links between the side drives.

All rigid supporting surfaces having good sliding properties are suitable as the support. These may be, for example, the following parts:

-   -   Roller tracks     -   Ball tracks     -   Sliding materials (e.g., plastics, non-ferrous heavy metals)     -   Air cushions     -   Hydrodynamic bearing of the individual links     -   Hydrostatic bearing of the individual links

In principle, it is also possible to equip each of the links with rollers or ball casters.

To improve the static friction, the rollers may also be pressed onto the driving rollers with the aid of lateral rollers. The rollers may also be designed as toothed wheels. In this case, the individual links also have a tooth profile with which the driving wheels may engage.

If a link conveyor is used, it is also possible to equip the underside of individual or all links with a round driving element, for example. The driving element is then gripped with the aid of a worm gear or a guide wheel and advanced by the necessary layer thickness.

If the individual links are equipped with a driving element, it is also possible to use a reversing linear drive, which repeatedly grips and positions the driving element by means of a gripper. This device may be provided with a particularly rigid design using simple means.

In principle, a spring-supported barbed hook may also be used instead of an active gripper, similarly to a one-way bearing.

Switchable vacuum grippers or magnets or hook-and-loop fasteners are also suitable. They may also be inserted in such a way that they engage with the belt in a rotating or oscillating manner. A preferred position would then be within the chain.

A particularly preferred embodiment of the invention lies in the use of a discontinuous conveyor line with the aid of a step conveyor. The transported material is moved along the entire length in discrete steps. One preferred form of a conveyor mechanism of this type includes a lever system in the form of a four-bar linkage, which is driven in a rotary motion at one of the linkage points. A rigid supporting surface is situated on the side at a distance from the lever mechanism. The movement sequence begins with the resting position of the transported material on the supporting surface. When the four-bar linkage rotates, a lever of the device will receive the load of the transported material, lift the transported material and place it back down on the supporting surface after a discrete distance has passed. The transported material must travel a horizontal distance on the supporting surface before the process starts over.

In the sense of the invention, “step conveyer” is to be understood as follows: a model or component is built in layers and transferred from a first position to a second position with the aid of a step conveyor device, this process continuing or being repeated in steps, and the component thus being subjected to step-by-step layering. It is possible that the process takes place in a longitudinal direction. Alternatively, the step conveyor device or the method may be designed in such a way that a repetition of the transfer from position 1 to position 2 and then back to position 1, etc., takes place. According to the invention, the step conveyor may be used to transfer the components, which have a weight of several hundred kilograms to several hundred tons, without distortion. The feed of each transfer may be from several centimeters to several meters, depending on the device and the method of the layer building method. The feed or transfer speed may be 0.5 to 20 m/min. or 0.1 to 15 minutes per cycle. The step conveyor may have a fixed frame, including guide rollers, a mobile frame on lifting rollers and a drive. The drive may have a mechanical, pneumatic or hydraulic design for the purpose of achieving the feed or the lift. For example, the mobile frame is lowered at the start position and the building plate with the model to be constructed is lowered onto the fixed frame with the aid of, e.g., hydraulics (a first position) and moved forward in one direction in order to be lowered again after the transfer (a second position). This procedure may then be repeated cyclically. The building plate is lifted and lowered again at the start and end of the direction of movement. The transfer process may be controlled from a central unit, e.g., a computer, and be coordinated with the other components and work steps for layering the component, such as application of layers and selective solidification or selective application.

The advantages of an approach of this type lie in a simple structure of the conveyor system, the ability to support and to move the transported material over the entire length. In addition, the structure may be designed to be extremely resistant to sagging due to loading by the weight of the transported material.

If multiple lever systems of this type are built next to each other, loads of greater width may also be reliably conveyed. The only requirement for the transported material: it must be stiff enough to bridge the distance between the lever systems in a freely supported manner. Flexible or fragile transported materials may also be transported with the aid of carrier systems such as palettes. If the transported material is to be moved horizontally without any vertical movement, the lever system may be equipped with linear actuators instead of the rotatory drive. In other words, the transported material again rests on a lever. Another lever moves against the transported material perpendicularly to the conveyance direction. The first lever is then lowered, and the second lever receives the load and shifts it by a discrete length in the direction of conveyance. The first lever then is raised again against the transported material and receives the load, while the second lever is lowered in order to move back into the initial position. To distribute the weight load better, a lever system of this type may comprise multiple levers situated side by side, which mesh with each other like two grates. Since the levers should have a certain distance from each other for reasons of reduced friction, a coverage must take place over the gaps between the levers if the transported material has small components, as in this case. This may be achieved, for example, by laying down a foil. If the transported material is a high-density particulate material, as in the present case, the foil must only be tensile, since the force of the weight is sufficient to hold the foil in position. The foil may be guided continuously over the device in the form of a belt as well as at the two ends of the device with the aid of foil rolling and unrolling mechanisms.

In another preferred embodiment, the sealing takes place via a link apron, which is guided over the lever mechanism.

A lift/thrust device made of two liftable grates has proven to be particularly advantageous for transporting a link apron or a conveyor belt.

A grate is assembled from parallel plates or rods which are oriented in the feed direction.

At least two grates engage with each other in such a way that each grate is positioned vertically and is able to carry the link apron. At least one of the two grates must be positioned in such a way that it may be moved in the feed direction.

During the building process, both grates are extended all the way with the aid of linear actuators (e.g., pneumatic cylinders, spindles), so that they are situated at the same height and both carry the conveyor belt (link apron). For transporting, one grate moves down, so that the only grate carrying the conveyor belt (link apron) is the one which is able to position it in the feed direction by means of another actuator (thrusting grate). Once the grate has positioned the conveyor belt (link apron) in the thrust direction, the other grate (lifting grate) moves out. When the lifting grate comes to rest, the thrusting grate moves downward again and subsequently returns to its vertical starting position.

In principle, the repositioning of the thrusting grate may also take place in the thrust direction after multiple individual steps, if the traveling distance of the linear actuators permits this. In this case, the thrusting grate is lowered and returned to the starting position only after multiple individual steps have been completed. This procedure may be advantageous for the purpose of reducing positioning errors, e.g., due to the reversing play of the linear actuators.

This system is absolutely rigid with respect to a conveyor belt, and precise positioning may take place simultaneously in both feed directions.

Another advantage of the system lies in its easy scalability, both in the feed direction and also transversely thereto, e.g., by widening the grates or arranging multiple systems in a row.

The structure may preferably have grates, and it is also possible to lift only the thrusting grate or a thrusting platform by a minimal amount. Minimal lifting in this case means lifting the thrusting grate or a thrusting platform only until the force of the weight produces the corresponding frictional engagement between the thrusting grate and the conveyor belt. The thrusting grate or a thrusting platform subsequently positions the conveyor belt horizontally. If the conveyor belt sags transversely to the conveyance direction, it may, under certain circumstances, fail to be fully lifted. The remaining supporting areas are then preferably designed to have good sliding properties. In these areas, air cushions or rollers may be mounted on the link apron itself or on the supporting surface.

Conveyor belts which are driven by means of frictional engagement or a form fit (similarly to a toothed belt) are also suitable up to a certain width. It would also be possible to incorporate driving elements into a flexible conveyor belt. Electrically conductive windings, which are incorporated into the belt, would also be possible, so that the entire belt is driven by means of self-inductance, similarly to a three-phase motor.

To avoid sagging in particularly wide belts, intrinsically rigid inserts may be incorporated transversely to the feed direction.

Another option according to the invention is to apply the particulate material feedstock on individual plates. The plates could be moved with the aid of the same transport systems as for link conveyors (see above). For continuous building, the transportation of the built-upon plates back to the start after unpacking must be ensured. This may be accomplished with the aid of robots or conveyor belts.

However, it is also possible to transport the individual plates on a rail system.

The plates may be supported individually, e.g., on rollers or air cushions, and transported into the system.

For automation, each plate may be equipped with its own intelligent drive. All information on the particular building project may be stored therein, and it may communicate with the building device and the warehouse.

The methods described above may also be used for conveyor belts and link conveyors which are rolled off of and onto rollers. A design of this type advantageously permits uninterrupted operation.

To store as many parts as possible, spiral conveyor belts may also be used, similarly to those in spiral freezers.

In principle, both open and closed belts in the form of foils or sheets may be used to seal link aprons. These sealing belts may be inserted by rollers in an open or closed manner.

Rotating plates, on which the material cone is applied tangentially, are also conceivable.

It would also be possible to produce a truncated cone on a rotating plate. The coater and the tool for selective solidification (e.g., the print head) move axially away from the rotation axis synchronously with the rotary motion of the plate.

In one particularly preferred device or method for producing components by 3D printing, according to the invention, a coater and a solidification unit for selective solidification are combined with a circular building platform (see FIG. 12). The first end and the second end are to be understood in such a way that a process start exists (first end), at which the particulate material application takes place, and a process end exists (second end), at which the component is finished or the finished components are preferably unpacked. The selective solidification may take place in the process with the aid of chemical methods (selective solidification with the aid of a chemical binder) as well as using methods such as selective laser sintering or laser melting (SLS, SLM). The circular building platform may also be combined with devices for the selective application of material, such as Fused Deposition Molding (FDM) and other methods known to those skilled in the art for the selective application of material to predetermined areas.

This preferred device according to the invention or the production method have the further advantage that the components are produced on a single rotating building platform, and the component thus does not change its position on the building platform, whereby the production also takes place without distortion. This is advantageous, in particular, when producing large and heavy components. The method may be carried out in batches or continuously. During continuous operation, a method step of a continuous unpacking operation, using means which are known to those skilled in the art, is combined with other device parts and method steps and coordinated therewith.

DESCRIPTION OF THE FIGURES

FIG. 1 shows a preferred structure according to the invention, including a closed conveyor belt (e.g., link conveyor) (7) and an open sealing belt (6). The conveyor belt is able to bear the great weight of the particulate material cake while the cover belt is being unrolled and should only prevent the conveyor belt from coming into contact with the particulate material cake. The conveyor belt is unrolled from a roller and rolled up again behind the conveyor belt. The cover belt may be fed by means of frictional engagement on the conveyor belt or by winding up.

FIG. 2 shows a preferred link conveyor according to the invention, including hinges which permit mobility only in one direction. The link conveyor is moved by a roller track in this case. Only one, multiple or all rollers may be driven.

FIG. 3a shows a preferred transport unit according to the invention, comprising conveyor belt (7) (preferably a link conveyor as in FIG. 2), which is driven laterally by driving rollers (14) and is supported on small rollers (15) in the middle.

FIG. 3b shows a similar structure, in which conveyor belt (7) rests on continuous driving rollers (17) over its complete width. To achieve a better frictional engagement between the driving rollers (14) or driving cylinders (17) and the conveyor belt (7), pressing rollers (13) press the conveyor belt onto the driving rollers (14) or driving cylinders (17).

FIGS. 4a and 4b show a preferred structure according to the invention, in which the driving rollers (14) are driven by a shared driving belt (18). Conveyor belt (7) may then rest on the driving belt and be additionally supported. In FIG. 4a , the middle of conveyor belt (7) is supported on sliding elements (19) made of, e.g., plastic. In FIG. 4b , the middle of the conveyor belt is carried by air cushions (20).

FIGS. 5a through 5c show a structure according to the invention, comprising a link conveyor (7), which has a gripping element (22) on each link. A gripper, which repeatedly grips and positions a gripping element, passes beneath the link conveyor. The sequence is gripping and positioning (FIG. 5a ), opening the gripper (FIG. 5b ), returning and regripping a link (FIG. 5c ).

FIG. 6 also shows a structure according to the invention, including a link conveyor (7), which has a gripping element (22) on each link, according to the invention. In this case, gripping elements (22) are positioned by a rotating worm drive (24).

FIG. 7 shows an oblique view of a preferred feed system according to the invention, including raised grates according to the invention.

FIGS. 8a through 8c show the sequence of the feed system from FIG. 7, from the front and from the side in each case, according to the invention.

FIG. 8a shows the starting position when both lifting grate (26) and thrusting grate (27) carry the conveyor belt. In FIG. 8a , lifting grate (26) has been extended and thrusting grate (27) subsequently lowered.

In FIG. 8b , lifting grate (26) has been lowered so that only thrusting grate (27) carries conveyor belt (7). Thrusting grate (27) then moves conveyor belt (7) into its next position.

In the lowered state, thrusting grate (27) returns to its starting position, as illustrated in FIG. 8 a.

FIG. 9 shows a preferred structure according to the present invention with self-propelled building platforms (31). They are moved into building device (32).

FIGS. 10a through 10c show additional preferred embodiments according to the invention. In this case, the feedstock is not produced linearly but rotatorily. The process begins at a first position or end and ends at a second position or end. FIG. 10b is a view of FIG. 10a from above. FIG. 10c is a side view of FIG. 10b of the cone printer according to the invention, on sectional plane A-A. (33) designates the outwardly oriented movement of coater (1) and solidification unit (2), which is indicated using directional arrows, the method being carried out on building platform (34), and a particulate material feedstock (3) being generated and components [produced], e.g., component (5), following solidification. For this purpose, round building platform (34) is rotated, while coater (1) and the print axis move away from the rotation axis. Coater (1) is rotated 90° with respect to the other preferred devices of the invention described above and may be operated continuously. Solidification unit (2) may also work continuously, whereby a plurality of components may be produced in this manner on one building platform (34) in one operation (batch). A build cone (21) may be used to start the system. The alpha angle may be changed, depending on the particulate material, and thus be optimally adapted to the particular particulate material used. This device type requires the data for the molds for the components to be produced to be skewed not only linearly but also on the basis of polar coordinates. The dimensions of the cone printer and the building platform as well as the device as a whole may be selected in such a way that both very small and very large and heavy components may be produced without distortion.

FIG. 11 shows a preferred building device (32) according to the invention, to the end of which an unpacking area, including a roller track (35), is connected. The finished components are deposited directly onto the roller track. Loose particulate material may run off between the rollers and thus support unpacking. The roller track may be driven or it may run passively.

FIG. 12 shows a preferred building device according to the invention with a rotating building platform (34). Coater (1) and solidification unit (2) move only translatorily, while building platform (34) continues to rotate layer by layer and thus continuously builds up material feedstock (3). In another preferred embodiment, the device in FIG. 12 may be configured in such a way that it is combined with an unpacking station or an unpacking operation in an arbitrary position. Finished components (5) are shifted to a position (36) inside or outside or below or above building platform (34) and freed of the remaining loose particulate material simultaneously or in another work step. The process begins at a first position or end, e.g., at the point of the first particulate material application, and ends at a second position or end, e.g., upon completion of the component or preferably at the point of unpacking. The loose particulate material may be resupplied cyclically to the further continuous process. The particulate material supply is thus limited to the quantities which are removed from circulation in the form of components and any non-reusable quantities.

FIGS. 13a through 13f show a drive for belts or link aprons with lifting grates (26) and thrusting grates (27) according to the principle of the step conveyor. Thrusting grate (27) moves on lever arms which swivel back and forth. Lifting grate (26) is raised on the return swiveling motion.

FIGS. 14a through 14d show a drive for belts or link aprons with lifting grates (26) and thrusting grates (27) according to the principle of the step conveyor. Thrusting grate (27) moves on rotating lever arms.

FIGS. 15a through 15d show a drive for belts or link aprons with lifting grates (26) and thrusting grates (27) according to the principle of the step conveyor. A vertical lifting of lifting grate (26) alternates with an inclined lifting of thrusting grate (27).

LIST OF REFERENCE NUMERALS

-   1 Coater -   2 Solidification unit -   3 Powder cake/particulate material feedstock -   4 Tunnel wall -   5 Component (being built) -   6 Roller for cover belt -   7 Conveyor belt (e.g., link conveyor) -   8 Linear unit -   9 Build space -   10 Link with hinge -   11 Driving cylinder -   12 Cylinder bearing -   13 Pressing roller -   14 Driving roller -   15 Bearing roller -   16 Motor -   17 Conveyance direction -   18 Driving belt (e.g., toothed belt) -   19 Sliding element -   20 Air cushion -   21 Gripper -   22 Gripping element -   23 Linear feed -   24 Worm wheel -   25 Frame -   26 Lifting grate -   27 Thrusting grate -   28 Linear bearing -   29 Lifting unit for lifting grate -   30 Lifting unit for thrusting grate -   31 Self-propelled building platform -   32 Building device -   33 Direction of movement of the coater and the solidification unit -   34 Rotating building platform -   35 Roller track -   36 Unpacking area 

What is claimed is:
 1. A device for producing three-dimensional models, comprising: i. a build platform for receiving layers of a particulate material, wherein the build platform is a portion of a conveyor; ii. a drive unit for driving the conveyor in a conveyance direction; iii. a dosing unit over the build platform for providing the layers of the particulate material; and iv. a solidification unit over the build platform for selectively solidifying the particulate material; wherein the build platform has a first end proximate a region where the particulate material is received and a second end in the conveyance direction; wherein a distortion of the three-dimensional model during a conveyance on the conveyor is reduced by one or any combination of the following: a. the conveyor is supported by a rigid supporting surface; or b. the conveyor is a link conveyor including links having a hinge with a stop, wherein the stop causes the conveyor to be rigid and sagging is prevented between the first and second ends; or c. the conveyor includes a conveyor belt supported by spaced apart cylinders or rollers.
 2. The device of claim 1, wherein the device includes the conveyor is supported by a rigid supporting surface
 3. The device of claim 2, wherein the rigid support surface includes one or more sliding elements, wherein the sliding element is elongated in the conveyance direction.
 4. The device of claim 3, wherein the sliding element has a plastic surface and the conveyor slides over the plastic surface.
 5. The device of claim 2, wherein the conveyor is driven by a plurality of spaced apart drive rollers.
 6. The device of claim 5, wherein the device includes pressing rollers that press the conveyor onto the drive rollers.
 7. The device of claim 1, wherein the conveyor is a link conveyor including links having a hinge with a stop, wherein the stop causes the conveyor to be rigid and sagging is prevented between the first and second ends.
 8. The device of claim 7, wherein the link conveyor includes links having a gripper element and the drive includes a linear feed with a gripper for gripping the gripper element and moving the link conveyor in the conveyance direction.
 9. The device of claim 8, wherein each link includes a gripper element.
 10. The device of claim 7, wherein the link conveyor includes links having a gripper element and the drive includes a worm wheel, wherein a rotation of the worm wheel moves the link conveyor in the conveyance direction.
 11. The device of claim 10, wherein each link includes a gripper element.
 12. The device of claim 1, wherein the conveyor includes a conveyor belt supported by spaced apart cylinders or rollers.
 13. The device of claim 12, wherein the conveyor belt is driven at the same speed at spaced apart drive locations.
 14. The device of claim 13, wherein the drive unit includes a driving belt.
 15. The device of claim 14, wherein the driving belt is a toothed belt.
 16. The device of claim 13, wherein the conveyor belt is supported by the cylinders and each of the cylinders is driven at the same speed.
 17. The device of claim 13, wherein the conveyor is supported by a middle support including an air cushion.
 18. The device of claim 13, wherein the conveyor is supported by a middle support including friction bearings.
 19. The device of claim 13, wherein the conveyor is supported by a middle support including rollers or ball casters.
 20. The device of claim 13, wherein the conveyor belt includes lateral edges, wherein the lateral edges are both positioned between spaced apart pairs of driving cylinders and cylinder bearings, wherein each driving cylinder-cylinder bearing pair independently drives the conveyor belt.
 21. The device of claim 13, wherein a single motor drives each driving cylinder.
 22. A method of constructing one or more three-dimensional models using the device of claim 1, comprising the steps of: i. applying layers of a particulate material on the build platform using the dosing unit; ii. selectively solidifying the particulate material using the solidification unit; and repeating the steps until the three-dimensional model is produced; wherein the build platform is a portion of a conveyor and the three-dimensional model is conveyed on the conveyor; wherein a distortion of the three-dimensional model during a conveyance on the conveyor is reduced by one or any combination of the following: a. the conveyor is supported by a rigid supporting surface; or b. the conveyor is a link conveyor including links having a hinge with a stop, wherein the stop causes the conveyor to be rigid and sagging is prevented between the first and second ends; or c. the conveyor includes a conveyor belt supported by spaced apart cylinders or rollers. 